Adelaide19.6 Discharge from urban water system to irrigation scheme

Supporting information

a. Discharge from urban water system to irrigation scheme

The volume (17,322 ML) reported in the water accounting statements is the volume of recycled water supplied from SA Water's wastewater treatment plants (WWTP) to the irrigation water supply system within the Adelaide region in the 2011–12 year. This volume included recycled water supplied from Christies Beach WWTP and Aldinga WWTP to the Willunga Basin Water Company (WBWC) and recycled water supplied from Bolivar WWTP to the Virginia Pipeline Scheme. The following table details the volume supplied from each WWTP to the respective irrigation scheme.

Recycled water supplied to irrigation schemes in the 2011–12 year

Wastewater treatment plant (WWTP)

Volume of recycled water supplied to the irrigation scheme (ML)

Bolivar WWTP

14,900

Christies Beach WWTP

2,244

Aldinga WWTP

178

Total

17,322

Barossa Infrastructure Limited does not receive recycled water from Adelaide's urban water system.

b. Recycled water system overview

The recycled water system is one of three sub-components of Adelaide's urban water system. The three sub-components are the:

urban water supply system

wastewater system

recycled water system.

In the Adelaide region, the majority of wastewater treatment plants produce recycled water which is subsequently provided to users (including irrigation schemes) or used on-site.

During the 2011–12 year, approximately 75% of the recycled water produced was provided to the region's irrigation schemes (line item 19.6). Approximately 11% of recycled water was used on-site at wastewater treatment plants, predominantly for on-site in-process uses (part of line item 19.4). The remaining recycled water produced in Adelaide was supplied for use; 3,159 ML was supplied to urban water system users (part of line item 19.4).

The following figure presents the inflows and outflows associated with the recycled water system. A very small misbalance (0.6%) is shown, due to the difference between the volume of recycled water produced and the volume of recycled water supplied for use, and can be attributed to metering inaccuracies and unaccounted losses.

For more detail on a particular flow associated with the recycled water system, refer to the line item notes. Note that volumes annotated with a * indicate flows between urban sub-components and are not reported in the Account 2012. As such, these flows do not have an associated line item number or note.

Schematic diagram of water inflows and outflows for Adelaide's wastewater system during the 2011–12 year; line item numbers are provided in brackets

Quantification approach

Data source

WWTP records.

Provided by

SA Water.

Method

The 2011–12 volume of recycled water transferred from Bolivar, Christies Beach and Aldinga WWTPs to the irrigation scheme was supplied from WWTP records held by SA Water. The volume represents metered outflows that are manually read and recorded by plant operators.

Assumptions, limitations, caveats and approximations

Nil.

Uncertainty information

The uncertainty estimate is not quantified.

Comparative year

This line item corresponds to line item 12.4 'Urban water discharge to irrigation scheme' reported in the 2011 Account.

The 2010–11 year volume reported in the 2011 Account was not restated to include the volume transferred from Aldinga WWTP to WBWC as the information that this flow occurred was received late and the data could not be sourced on time for this report. The difference in the 2010–11 year line item volume, however, would not have been material.